Field of the Invention
The invention pertains generally to electromagnetic injector valves and is more particularly directed to a fast acting high flow rate injector valve with predictable fuel spray pattern.
Electromagnetic fuel injection valves are gaining wide acceptance in the fuel metering art for both multipoint and single point systems where an electronic control apparatus produces a pulse width signal representative of the quantity of fuel to be metered into an internal combustion engine. The injectors operate to open and close pressurized fuel metering orifices leading to the air ingestion paths of the engine by means of a solenoid actuated armature responding to the electronic signal. The quantity of fuel injected can then be precisely tailored to the operating conditions of the engine by controlling the fuel pressure, orifice size, and the duration of the injector on time. Because of recent advances, electromagnetic injectors are becoming very precise in their metering qualities and very fast in their operation. With these advantages the electromagnetic fuel injector valve will continue to assist the advances in electronic fuel metering which have improved economy, reduced emissions, and aided the driveability of the internal combustion engine.
Present electromagnetic injectors are usually divided into two sections wherein the first section or the stator means generates a magnetic force to control the second section or the valve assembly which meters the fuel. The two sections are operably coupled by a magnetically attractable armature physically connected to a valve member. The valve member is normally biased against a valve seat by a closure spring in an off mode and opens in response to the magnetic force.
Many of these injector valves have fuel under pressure input to an entry port at the stator end of the injector. The fuel then flows by a generally concentric central path through the body of the injector to the valve assembly. These structures are usually termed "top feed" injectors. Other injector structures have been made whereby lower pressures of input fuel may be made to the valve assembly end. These structures are usually termed "bottom feed" injectors. The lower fuel pressure of the "bottom feed" injector reduces the demand for a more expensive fuel pump and pressurizing system which is necessitated in the "top feed" injector. Further, with a "bottom feed" injector, more flexible mounting procedures may be used to advantage. It is known that such "bottom feed" injectors can be utilized either in single point or multi-point systems.
Examples of "bottom feed" injectors and their mounting structures in two advantageous single point systems are found in U.S. Pat. Ser. No. 956,693 filed on Nov. 1, 1978 in the name of W. B. Claxton, and U.S. Ser. No. 875,832 filed on Feb. 7, 1978 in the name of G. L. Casey; both of which applications are commonly assigned to the assignee of the present application and the disclosure of which is hereby expressly incorporated herein by reference.
These injectors meter fuel by the length of time that the valve mechanism is open and have a static fuel flow rate dependent upon the size of the exit orifice. Relatively small changes in the metering orifice size can substantially change the flow rate of the injector and thus the exit orifice size must be precisely controlled. Claxton discloses a means by which the static flow rate of the fuel injector may be tailored after assembly without reboring the exit orifice if it is off-sized. Still other injectors have prior to this been expensively remanufactured if the static flow rate is out of tolerance.
Even with this flow rate trim, the Claxton injector after normal use may deviate from its calibrated static fuel rate. Contaminants from evaporating fuel and foreign particles in the air flow may lodge in the exit orifice of the injector creating a modification to the flow rate. There is nearly always some contamination build-up on the injector tip after extensive use in hostile engine environment. This is especially true in a low pressure "bottom feed" injector where the force of the fuel through the exit may not be enough to clean contamination and debris from the exit orifice. It would, therefore, be highly desirable to obtain the advantages of an injector trim and orifice metering while not basing the injector flow rate on the exit orifice diameter which can change with contamination.
Further, Claxton discloses a fast-acting valve which can be dynamically cycled into the millisecond range because of its low mass armature and needle valve combination. Another low mass armature and the needle combination is illustrated in a U.S. application Ser. No. 940,522 filed on Sept. 8, 1978 in the names of J. C. Cromas, et al. and assigned commonly to the assignee of the present application, the disclosure of which is hereby expressly incorporated herein by reference.
Although these injector valves have armature and needle valve combinations which are particularly low in mass and work well, they do require machining of the bearing surfaces of their medial sections to produce the desired results. Highly machined and smooth medial sections are required because the bearing surfaces must slide concentrically to center the valve member into a conical valve seat securely for sealing purposes.
Another fuel injector having a low mass armature and valve member combination is disclosed in a U.S. Pat. No. 4,030,688 issued in the name of A. M. Kiwior on July 21, 1977 and which is commonly assigned with the present application. Kiwior discloses the use of a ball valve on the end of a flexible stem mating with a conical valve seat that has been coined. The armature and valve member combination of this injector also utilizes bearing surfaces on the medial section for guiding purposes, although it has a self-centering valve. Therefore, this injector valve member and armature combination is fairly complicated in structure primarily suitable for a "top feed" injector. It would be desirable to provide an "end feed" injector with a low mass valve member and armature combination that is self-centering and does not necessitate highly machined bearing surfaces on its medial section.
While all of the injectors discussed to this point can be used in either single point or multi-point applications, it appears that single point applications will become more and more prevalent. One such single point system gaining in popularity today requires electromagnetic injector that is mounted above the throttle blade of the air ingestion path for the internal combustion engine. When mounted in such a manner, the most desirous spray pattern for the injector is either full atomization or a wide angled "hollow cone" type of pattern. The hollow cone spray pattern is termed such because much of the injected fuel is contained between an inner and outer cone angle which have their apexes substantially at the point of injection. The hollow cone pattern is advantageous in above throttle blade injection because it does not wet the sides of the throttle bore or the throttle plates substantially and directs the fuel into the turbulent air between the throttle blade and bore wall for excellent mixing and atomization prior to engine ingestion.
One of the methods of generating a wide angle spray is to generate a swirling or a vortex from the fuel injector which spreads the fuel substantially uniformly between the angles desired. In the application by Claxton a number of vortex generation techniques that are useful to provide wide angle sprays are disclosed. Further, U.S. Pat. No. 3,241,168 issued to Croft illustrates a swirl generation means with a swirl chamber in an electromagnetic fuel injector.
Croft and Claxton, however, generate wide angled spray patterns that are difficult to control at lower pulse widths for the injectors. Both references have swirl chambers that have relatively large residual volumes when the injector is off. When the injector is opened there is a delay before the spray pattern is regenerated and the vortex can be built up. Croft attempts to solve this problem by using a complicated recirculation path to continaully move fuel through the swirl chamber when the valve is closed. These injectors also meter fuel with their exit orifices which, as has been explained before, makes them subject to contamination problems. The valve members of these injectors further extend into the valve seats a substantial length and this extension tends to disturb the vortex generated therein. The swirling fuel tends to drag along the surfaces of the valve tip and lose momentum.
It would, therefore, be desirable not only to provide an injector with a swirl chamber having a minimum residual volume, but also one including an injector valve member that does not extend substantially into the valve seat.
Since one would prefer an injector structure that could be used in either single or multipoint injection and a multiplicity of both types of designs are being proliferated, it would be highly desirable to be able to control the spray angle of the injector in the preferred hollow cone pattern over a wide range. Generally, for single point applications the farther away from the throttle blade an injector is, the narrower the spray angle. Also, a very narrow spray angle can be utilized for most multipoint applications. Wider spray angles can be used for closer placement of the injector with respect to the throttle blade in many other single point applications.
Wide control of the spray angle with a single common structural element of the injector is difficult for a low pressure and high flow rate valve. One method of spray angle control is illustrated in the application by Cromas, et al. where a protected pintle that has a deflection surface perpendicular to the spray axis of the injector is used. The distance away from the exit orifice and the diameter of the deflection surface varies the spray angle over a wide range of injector pressures and flow rates. The deflectiodesirable to generate a controllable spray pattern over wide ranges of pressures and flow rates without the expense of the deflection pintle.